The invention relates generally to heat generating and supporting devices used in baking food items having a dough crust. Such devices include a package having a closure and tray or platform suitable for use during cooking and more specifically include closure and tray or platform devices suitable for use in baking processes in microwave ovens. More specifically, the invention relates to microwave cooking packages which enclose the food item on all sides and are capable of heat generation and heat control during baking methods. More specifically, the invention is directed to microwave cooking packages which are designed to obtain even and effective heat generation for all dough surfaces.
BACKGROUND OF THE INVENTION
Microwave ovens differ substantially from conventional radiant heating ovens in their heating mechanism. In a conventional radiant oven, heat energy contacts the exterior surface of the food and its container during cooking. The heat energy moves inward as the food cooks. Consequently, food cooked in a conventional oven is typically hotter on the exterior and cooler in the center. Convection ovens, in which air circulation is improved via an integral fan placed in front of the heat source, is similar to a conventional oven. Of course, cooking times in a convection oven may be lower due to its improved heat transfer characteristics.
In microwave cooking, polar molecules (such as water) in the food adsorb microwave energy and release heat. Microwave energy typically penetrates further into the food than does heat energy and heats water molecules throughout the food. Water may be expelled from the food resulting in a dry texture. On the other hand, if water vapor is not dissipated, the food tends to become soggy. In either case, the food develops an unpalatable texture. There is a need for a package for food, especially dough enrobed food items, which conveniently enables cooking in a microwave oven without adversely affecting taste or texture.
Further, the air temperature within the microwave oven is substantially lower than conventional ovens. Microwave ovens can also have a hot spot or spots characteristic of uneven energy distribution in the oven. As a result, foods cooked in a microwave oven are often warmer in unpredictable positions. As a result, it is more difficult to obtain the surface temperatures necessary for Maillard and other browning reactions. To attain the necessary temperatures and to insure even baking in a microwave oven, the food must be heated to greater temperatures. In order to solve this problem, the use of susceptor materials has gained favor.
Conventional susceptor materials are well understood and are typically incorporated in packaging that is heated by incident microwave energy. Typically, in microwave cooking applications, a suitable susceptor material is placed as a layer upon a packaging substrate such as paper or paperboard. Typical susceptor materials include a thin layer of particulate metal such as aluminium. These are referred to as metallized susceptors. Other susceptor materials are classified as non-metallized, and include materials which can be sprayed, coated or printed onto the paper or paperboard substrate. Susceptor materials have had problems in the past, such as development of hot spots and runaway heating.
A problem which remains involves cooking frozen rising dough pizza crusts. While a certain amount of heat is necessary to cook and brown the crust, excessive heat generation underneath the crust can result in puffing or ballooning of the uncooked or partially cooked crust during baking. This can cause uneven cooking and can cause toppings to become dislodged, or even fall completely off the pizza. Further, this ballooning or puffing can be considered very undesirable by the ultimate consumer.
A second cause of ballooning or puffing is excess gas or water vapor generation during baking. Previous attempts at ventilation have been directed to cooking food such as pizzas within a cardboard or paperboard box which has one or more ventilation holes provided in packaging positioned above or around a heated food item. Examples of this include Kuchenbecker, U.S. Pat. Nos. 4,096,948 and 4,592,914. However, these patents both describe structures in which the food is placed inside, rather than atop the structure. This does nothing to vent the underside of the cooking pizza crust. A two part carton for handling and cooking food items wherein the top panel of the carton has a microwave reflective layer to shield food contents from microwaves and provides for venting moisture between edges of the upper and lower parts of the carton is disclosed by Brown, U.S. Pat. 4,567,341.
Further, these patents are silent as to the problem of excessive or uneven heat generation by microwave energy impinging on a susceptor layer. Attempts have been made to control heat generation. One method of doing so is to use an electrically conductive or xe2x80x9creflectivexe2x80x9d shield which limits the amount of microwave energy which is permitted to impinge on the susceptor material. Examples of this technique include Turpin, U.S. Pat. No. 4,190,757; and Lorence et al., U.S. Pat. No. 5,288,962. These are complicated, multi-piece devices, however.
Brastad, U.S. Pat. No. 4,267,420 describes a plastic wrap having a very thin coating thereon which controls microwave conductivity when a wrapped food item is cooked in a microwave oven. The wrap contacts all surfaces of the food item and does not provide for release of water vapor formed during cooking.
Bowen et al., U.S. Pat. No. 4,450,334 describes a cooking utensil suitable for baking pizza combining a microwave conductive pan mounted on a microwave transparent base having a separate microwave conductive cover removably supported by the base. The utensil does not form part of a package suitable for storage and handling of food items. The utensil is intended to provide uniform heating of pizza during microwave baking.
Peleg et al., U.S. Pat. No. 5,077,455 discloses an open-ended sleeve receptacle for microwave browning and crisping of a food item. The sleeve is made from microwave susceptor stock. The sleeve does not expose all sides of the food item to a susceptor surface. Further, the sleeve is intended to be assembled immediately prior to microwave cooking and is not suitable as a package for storage and handling of food items.
Another attempt at controlling heat generation is exhibited by Wendt et al., U.S. Pat. No. 4,927,991, in which an intact susceptor layer is used in conjunction with an electrical conductive grid. The grid serves to diffuse, or evenly distribute incoming microwaves. Specifically, this allows for control of the relative amounts of reflected, transmitted and absorbed power when used in with the suspected layer. However, this is a multi-piece structure. Further, the grid taught by Wendt fails to address the issue of venting.
Consequently, a need remains for a simple, easy to operate, package and cooking tray suitable for cooking foods such as frozen pizza and dough enrobed food items in a microwave oven which provides uniform browning of dough crust and venting of moisture so that the crust bakes without becoming soggy.
Accordingly, the invention is found in a microwave cooking package and tray suitable for cooking food. The package is particularly suited for cooking food items comprising a dough crust which must be baked and/or browned. The package comprises a laminate structure having a base forming a tray providing a food contact surface, a wall surface defining a cavity disposed on the base and a lid shaped and configured to rest on the wall and enclose the cavity wherein the laminate structure comprises a susceptor layer upon a backing material. A plurality of apertures are spaced through the laminate structure in an effective water vapor dissipating pattern. The package also has supports to provide a space between the package and the surface upon which it rests to dissipate water vapor. The pattern of apertures and the vertical supports cooperate to heat and vent the food being baked. Further, the apertures reduce the amount of the susceptor material and control direct heating.
In a preferred embodiment, the invention is found in a one piece package having a hingedly connected lid suitable for cooking food items by microwave heating such that the food item is enclosed on all sides by a susceptor layer. The lid has a latching tab positioned to cooperatively interact with a slot in a wall of the package to fix the lid in place when closed. The closed package provides dough enrobed food items with sufficient moisture during baking to maintain a chewy texture while the susceptor layer exposes the surface of the food item to substantially uniform heat to provide a brown and crispy crust. The tray structure on which the food item rests has a plurality of apertures. The apertures dissipate water vapor released from the portion of the food item in contact with the tray thereby reducing the tendency for dough at the interface with the tray to blister or balloon. The lid may also have one or more apertures to dissipate moisture released by particularly moist food items such as those comprising sauces and gravies.
In another preferred embodiment, the lid and base are not connected prior to assembling to form a package for cooking food items in a microwave oven. The base is a one piece tray having side walls defining a cavity disposed on the base. A plurality of apertures are spaced through the tray in a pattern effective to dissipate water vapor. The tray also has fold out verticle supports to provide a space between the package and a support surface in the microwave oven to aid with dissipating water vapor. The lid has two or more locking tabs configured to mate with locking slots in the base when the lid is positioned to form a package. A food item is placed on the tray formed in the base, the lid is positioned on the base and the tabs are inserted into the slots to hold the lid in place during storage, transportation and handling. The lid and base form a package having a laminate structure. The laminate structure comprises a susceptor layer upon a backing material. The package exposes all sides of a food item to a susceptor surface during cooking to promote uniform browning of crust surfaces.
In another preferred embodiment, the invention is found in a one piece cooking tray suitable for cooking food in a microwave oven having a oven floor, wherein the tray comprises a laminate structure comprising a susceptor layer upon a backing material, the laminate structure comprising a portion that can be formed into a support that can maintain the susceptor layer at a distance of at least about 4 millimeters from the oven floor; and a distribution of apertures through said laminate structure. The apertures are sufficient to permit venting and to control heat generation under the food being cooked.